The daughter of former Iranian president Akbar Hashemi Rafsanjani has been sentenced to six months in jail after being found guilty of "spreading propaganda" against the country's regime.

Faezeh Hashemi, a political activist and former member of the Iranian parliament whose views are close to those of the reformists, was informed of the court's verdict on Tuesday, Iran's semi-official Ilna news agency reported.

"She has been convicted on charges of making propaganda against the ruling system and has been sentenced to six months in prison," Hashemi's lawyer, Gholam Ali Riahi, told Ilna.

Riahi said Tehran's revolutionary court also banned Hashemi from belonging to any political parties and taking part in media or online activities for the next five years. She has 20 days to appeal.

She fell foul of the Iranian authorities after the disputed presidential elections in 2009 when she publicly supported opposition candidate Mir Hossein Mousavi and later participated in popular protests against the vote's results. At the time, she was briefly arrested in two separate occasions and barred from leaving the country.

Her conviction is believed to be the result of an interview she gave to an opposition website, Roozonline, in which she blamed regime supporters for harassing her in public.

Hashemi's criticism of the regime in recent years has led to an uproar among conservatives who believe that – as the daughter of a leading politician – she should back the official line, and not that of the opposition Green movement which the authorities now refer to as the "sedition".

Hashemi Rafsanjani is the head of Iran's expediency council which mediates between the parliament and the guardian council, a body that vets all parliamentary legislation.

In the past, he had a great deal of influence on Iranian politics but his authority has diminished since he lost the 2005 presidential election to Mahmoud Ahmadinejad.

Ahmadinejad played an instrumental role to undermine his rival by publicly making allegations of financial corruption against Hashemi Rafsanjani's family. After Ahmadinejad took office for the second time in 2009, Hashemi Rafsanjani was further sidelined. In March 2011, he stepped down as the head of Iran's expert's council, a powerful clerical body in charge of appointing and dismissing the supreme leader.

Iranian authorities last week blocked access to Hashemi Rafsanjani's official website in an unprecedented move against a man who was the protege of Ayatollah Khomeini, the founder of the Islamic revolution, and played a significant role in the appointment of Ayatollah Khamenei as the current supreme leader.

The spokesman for Iran's judiciary, Gholamhossein Ejeii, said on Monday that the website was filtered according to the country's computer crimes regulations. Other former high-ranking officials – including former reformist president Mohammad Khatami – have also seen their websites subject to censorship.

The sentencing of Hashemi Rafsanjani's daughter comes amid growing political tension before parliamentary elections in March, the first general vote in the country since 2009.

More than 5,000 people have registered as parliamentary candidates but only those approved by the guardian council will be allowed to run. Few reformists are reported to have put their names forward, while many opposition groups have called for a boycott of the vote. Opposition leaders Mousavi and Mehdi Karroubi have been under house arrest since February.

Nervous about the turnout, Iranian authorities said any attempt to mount a boycott of the election would be viewed as a crime. They specifically warned against any online efforts to organise a boycott.

In a separate incident on New Year's Day, the house of Iran's first post-revolution president, Abulhassan Banisadr, in exile in France, was broken into in what appeared to be a politically motivated incident. Banisadr has been critical of the regime in recent years.